JP6951857B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens and an imaging device having the zoom lens. More specifically, the present invention relates to a telescopic and compact zoom lens suitable for a photographing optical system of a digital input / output device such as a digital still camera or a digital video camera, and an imaging device having the zoom lens.

In recent years, imaging devices using solid-state image sensors such as digital still cameras have become widespread. Along with this, the performance and miniaturization of imaging lenses have progressed, and compact imaging device systems have rapidly become widespread. There is a strong demand for miniaturization of these imaging lenses as well as high performance. In particular, there is a strong demand for imaging zoom lenses such as telephoto zoom lenses that have a long focal length at the telephoto end.

In response to such a request, the zoom lens described in Patent Document 1 is a telephoto zoom lens having a zoom ratio of about 4 times and a focal length of about 600 mm at the telephoto end, which is equivalent to a 35 mm version, despite its small size. It has been realized (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-126850

By the way, in the zoom lens described in Patent Document 1, since the focus group is composed of a plurality of lenses, the aberration fluctuation at the time of focusing is suppressed, and high optical performance is maintained in the entire focusing range. .. However, since the focus group is heavy and the focus drive mechanism for driving the focus group is also large, it is insufficient in terms of weight reduction and miniaturization of the entire lens unit.

An object of the present invention is to provide a telephoto zoom lens and an imaging device capable of reducing the weight of the focus group while maintaining high optical performance and securing a flange back suitable for an interchangeable lens. be.

In order to solve the above problems, the zoom lens according to the present invention employs the following three types of zoom lenses.

The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side. , A zoom lens that changes the magnification by changing the air spacing between each lens group.
A focus group composed of one lens is provided after the third lens group.
The focus group is composed of a single lens having a negative refractive power.
When focusing from an infinity object to a nearby object, only the focus group is moved along the optical axis direction, and the following conditional expression is satisfied.

(1) −1.60 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(6) 0.39 <f1 / ft <0.70
(12-1) 1.80 <Bfw / (fw × tanωw) <3.00
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focal length fw of the first lens group: Focal length of the entire zoom lens system at the wide-angle end ft: Focal length of the entire zoom lens system at the telephoto end
Bfw: Air equivalent length from the most image-side surface to the image surface at the wide-angle end of the zoom lens.
ωw: Half angle of view of the most off-axis main ray at the wide-angle end of the zoom lens

The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side. , A zoom lens that changes the magnification by changing the air spacing between each lens group.
A focus group composed of one lens is provided after the third lens group.
The focus group has a convex shape on the side surface of the object.
When focusing from an infinity object to a nearby object, only the focus group is moved along the optical axis direction, and the following conditional expression is satisfied.

(1-1) −1.45 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(6-1) 0.481 ≤ f1 / ft <0.70
(9-1) 1.60 <f1 / fw <3.20
(13) −0.30 <fF / ft <−0.05
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focal length fw of the first lens group: Focal length of the entire zoom lens system at the wide-angle end ft: Focal length of the entire zoom lens system at the telephoto end fF: Focal length of the focus group

The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side. , A zoom lens that changes the magnification by changing the air spacing between each lens group.
A focus group composed of one lens is provided after the third lens group.
When focusing from an infinity object to a nearby object, only the focus group is moved along the optical axis direction, and the following conditional expression is satisfied.

(1) −1.60 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(5-1) 0.931 ≦ (Crff + Crfr) / (Crff-Crfr) ≦ 2.074
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens.
f1: Focal length of the first lens group
fw: Focal length of the entire zoom lens system at the wide-angle end
ft: Focal length of the entire zoom lens system at the telephoto end
Crff: Radius of curvature of the lens surface on the most object side in the focus group
Crfr: Radius of curvature of the lens surface closest to the image in the focus group

Further, in order to solve the above problems, the image sensor according to the present invention converts the zoom lens according to the present invention and the optical image formed by the zoom lens on the image side of the zoom lens into an electrical signal. It is characterized by being provided with an image pickup element.

According to the present invention, it is an object of the present invention to provide a telephoto zoom lens and an imaging device capable of reducing the weight of a focus group while maintaining high optical performance and securing a flange back suitable for an interchangeable lens. be.

It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 1 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the first embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of the first embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the first embodiment. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 2 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the second embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of the second embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the second embodiment. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 3 of this invention. It is a spherical aberration diagram, astigmatism diagram and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of Example 3. FIG. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of Example 3. FIG. 3 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the telephoto end of the zoom lens of the third embodiment.

Hereinafter, embodiments of the zoom lens and the imaging device according to the present invention will be described. However, the zoom lens and the imaging device described below are one aspect of the zoom lens and the imaging device according to the present invention, and the zoom lens according to the present invention is not limited to the following aspects.

1. 1. Zoom lens 1-1. Optical configuration The zoom lens (variable magnification optical system) of the present embodiment has a first lens group having a positive refractive force, a second lens group having a negative refractive force, and a positive refractive force in this order from the object side. It is a zoom lens that has a third lens group having a lens group and changes the magnification by changing the air spacing between the lens groups, and has a focus group composed of one lens after the third lens group. When focusing from an infinity object to a nearby object, only the focus group is moved along the optical axis direction, and the conditional equations (1) and (2) described later are satisfied.

The zoom lens of the present embodiment adopts the above configuration and satisfies the conditional equations (1) and (2) described later to maintain high optical performance and reduce the weight of the focus group. In addition, a telephoto zoom lens that can secure a flange back suitable for an interchangeable lens has been realized. In particular, the zoom lens adopts a telephoto type power arrangement, and by converging the incident light beam by the first lens group and diverging it by the second lens group, it is compared with the focal length while aiming for telephoto. This makes it possible to realize a compact zoom lens with a short optical length.

Further, in the zoom lens, even if a large negative refractive power is arranged in the second lens group, the second lens group is provided by the first lens group and the third lens group having positive refractive power arranged before and after the large negative refractive power. By increasing the lateral magnification of the lens, a telephoto zoom lens with a strong telephoto tendency can be obtained, and the zoom lens can be telephoto.

Here, in the zoom lens of the present embodiment, as described above, the first lens group having a positive refractive force, the second lens group having a negative refractive force, and the positive refractive force are sequentially applied from the object side. It is a zoom lens that has a third lens group and changes the magnification by changing the air spacing between the lens groups, and as long as the focus group is provided after the third lens group, the lens included in the zoom lens. The number of groups and the specific configuration of each lens group are not particularly limited. Hereinafter, a more preferable aspect of the focus group and a more preferable lens group configuration of the zoom lens will be described.

(1) Focus group The focus group is composed of one lens. Here, one lens means one lens generally called a single lens (spherical lens / aspherical lens). The aspherical lens includes a molded lens (made of glass or plastic) or a composite aspherical lens having an aspherical film attached to the surface, in addition to a lens whose surface has been precision-polished. That is, in the zoom lens, the number of lenses constituting the focus group is one, and the focus group consists of a bonded lens in which a plurality of lenses are joined without an air gap, or a plurality of lenses are connected via an air gap. A focus group composed of a plurality of lenses, such as an arranged focus group, is different from the focus group according to the present invention.

By configuring the focus group with one lens, it is possible to reduce the weight and size of the focus group as compared with the case where the focus group is composed of a plurality of lenses. Therefore, the drive mechanism (mechanical member) for driving the focus group can also be miniaturized, and the weight and miniaturization of the entire lens unit including the lens barrel of the zoom lens can be realized. In addition, since the weight of the focus group can be reduced, it is possible to realize quick autofocus.

Further, when the focus group is composed of one lens, the eccentricity error and the error of the air spacing between the lenses are compared with the case where the focus group is composed of a plurality of lenses arranged via the air spacing. Various manufacturing errors can be reduced. Therefore, it is possible to suppress a decrease in optical performance due to a manufacturing error, and it is possible to manufacture a zoom lens having high optical performance.

The refractive power of the focus group may be either positive or negative, but it is preferable to have a negative refractive power from the viewpoint of reducing the size of the zoom lens.

The focus group may be configured as one lens group that moves independently of the other lens groups at the time of magnification change, or is configured as a part of any lens group that constitutes the zoom lens. You may be. In the zoom lens, one lens group consists of lenses adjacent to each other, and the lenses included in the one lens group are assumed to have the same movement direction and movement amount in the optical axis direction at the time of magnification change. .. Further, the lens groups adjacent to each other are assumed to have different directions and / or amounts of movement in the optical axis direction at the time of magnification change. However, one lens group may be composed of only one lens. As described above, the single lens in this case refers to a single lens or an aspherical lens (glass molded lens or composite aspherical lens).

The fact that the focus group is formed as a part of any of the lens groups constituting the zoom lens means the following. For example, when the focus group is configured as a part of the third lens group, the focus group at variable magnification moves or is fixed together with the third lens group along the optical axis direction. Then, when focusing from an infinite object to a nearby object, only the lenses constituting the focus group among the lenses constituting the third lens group move along the optical axis direction. When the focus group is configured as a part of the third lens group, in the third lens group, in the lens group consisting of all the lenses arranged on the object side of the focus group, or in the third lens group. A lens group consisting of all lenses arranged on the image side of the focus group is called a partial lens group. The same applies to the case where the focus group is configured as a part of a lens group other than the third lens group.

In the zoom lens, the focus group may be provided after the third lens group, and the arrangement thereof is not particularly limited. As described above, the focus group may be configured as a part of the third lens group, or may be configured as a part of the lens group after the fourth lens group, or as a whole thereof. However, in order to reduce the size of the zoom lens and the entire lens unit, it is preferable that the focus group is provided on the image side of the third lens group. That is, it is preferable that the focus group is arranged after the fourth lens group. By providing the focus group on the image side of the third lens group having a positive refractive power, the light beam flux incident on the focus group can be converged by the third lens group. Therefore, it is possible to reduce the size and weight of the focus group in the radial direction. Therefore, for the same reason as described above, the zoom lens and the entire lens unit can be made smaller and lighter, and quick autofocus can be realized.

For the same purpose, in the zoom lens, the focus group is preferably arranged on the image side of the lens group or the partial lens group having a positive refractive power with an air gap. That is, when the focus group is configured as a part of the lens group after the third lens group, a lens group or a partial lens group having a positive refractive power is arranged on the object side of the focus group via an air gap. It is preferable to have. When the focus group is configured as one lens group after the third lens group, it is preferable that a lens group having a positive refractive power is arranged on the object side of the focus group via an air gap. In these cases, the lens group or the partial lens group arranged immediately before the focus group can further converge the light beam incident on the focus group, so that the weight and size of the focus group can be further reduced. can. Further, since the light beam incident on the focus group is converged, even when the focus group moves during scaling or focusing, it is possible to reduce the change in the angle of the light ray incident on the focus group during that time. That is, it is possible to suppress the aberration fluctuation accompanying the movement of the focus group, and the amount of aberration generated in the focus group is also reduced. Therefore, even if the distance to the subject is short, that is, even when the focal length is near-junction, a good aberration correction state can be maintained regardless of the focal length.

Further, in order to reduce the size of the zoom lens and the lens unit as a whole while achieving high performance of the zoom lens, it is preferable to provide at least one other lens group on the image side of the focus group. In a zoom lens, the diameter of the lens constituting the lens group arranged closest to the image side (hereinafter, referred to as "final lens group") generally constitutes the lens group arranged on the object side with respect to the final lens group. It is larger than the diameter of the lens to be used. By setting the focus group as a lens group other than the final lens group and arranging at least one or more other lens groups on the image side of the focus group, it is possible to further reduce the weight and size of the focus group. can. It is preferable that the final lens group is a lens group having a positive refractive power in order to realize a bright optical system having a small F number. Further, it is preferable that the final lens group is a lens group having a negative refractive power in order to realize an optical system having a short optical overall length.

(2) Lens Group Configuration Here, the zoom lens of the present embodiment may include the first lens group to the third lens group, and the focus group may be provided after the third lens group, and the zoom lens is configured. The number of lens groups to be used, the power arrangement, the position of the focus group, and the specific lens configuration of each lens group are not particularly limited. For example, the zoom lens may have a positive / negative / positive three-group configuration, and a part of the third lens group may be a focus group. However, as described above, since it is preferable that the focus group is provided after the fourth lens group, it is preferable that the zoom lens has a four-group configuration or more. Further, since the focus group is preferably a lens group other than the final lens group, the zoom lens preferably has a configuration of 5 groups or more.

Further, when the zoom lens has a 6-group configuration or more, the 4th lens group is a lens group having a positive refractive power, and the 5th lens group is a focus group, thereby further reducing the weight of the focus group. It is preferable because it can be miniaturized.

(3) Aperture The arrangement of the diaphragm is not particularly limited in the zoom lens. The zoom lens can obtain the effect according to the present invention regardless of the position of the aperture in the zoom lens. Further, the aperture may be fixed to the image plane or may be configured to be movable.

(4) Anti-vibration lens group The zoom lens may include a so-called anti-vibration lens group. Here, the anti-vibration lens group refers to a lens group composed of one or a plurality of lenses configured to be movable substantially perpendicular to the optical axis. By moving the anti-vibration lens group in a direction substantially perpendicular to the optical axis, it can be moved in a direction substantially perpendicular to the optical axis. As a result, it is possible to correct image blurring due to vibration during imaging such as camera shake. The anti-vibration lens group can be any one of the lens groups constituting the zoom lens. Further, the anti-vibration lens group may be a part of any one lens group constituting the zoom lens.

1-2. Operation Next, the operation of the zoom lens during magnification change and focusing will be described.

(1) Operation at the time of magnification change The zoom lens changes the magnification by changing the air spacing between each lens group. All the lens groups constituting the zoom lens may be moved along the optical axis direction at the time of magnification change to change the air spacing between the lens groups, or some lens groups may be fixed groups and the rest. The air spacing between the lens groups may be changed by moving the movable group of the lens group in the optical axis direction at the time of scaling.

For example, when scaling from the wide-angle end to the telephoto end, the air gap between the first lens group and the second lens group widens, and the air gap between the second lens group and the third lens group narrows. , Each lens group can be moved or fixed.

Further, in the zoom lens, if the first lens group is moved to the object side when the magnification is changed from the wide-angle end to the telephoto end, the optical total length of the zoom lens at the wide-angle end can be shortened. In this case, the lens barrel is configured to be expandable and contractible, for example, in a nested shape, and when the magnification is changed from the wide-angle end to the telephoto end, the lens barrel length is extended as the first lens group moves, and the lens barrel is extended from the telephoto end to the wide-angle end. If the lens barrel length is shortened at the time of variable magnification, the lens barrel length in the wide-angle end state can be shortened, and the lens unit can be miniaturized.

Further, if all the lens groups are movable groups at the time of magnification change, the position of each lens group is optimally moved according to the focal length, so that aberration correction can be performed satisfactorily in the entire magnification change range. .. Further, by setting the final lens group as a fixed group or a part of the lens groups as a fixed group, it is possible to reduce the weight and size of the drive mechanism for moving the movable group at the time of scaling. The weight and size of the entire lens unit of the zoom lens can be reduced.

(2) Operation during focusing The zoom lens focuses a focus group from an infinity object to a nearby object by moving the focus group along the optical axis direction. At this time, only the focus group is moved, and the other lens groups (including the partial lens group) are fixed in the optical axis direction. By configuring the focus group with one lens and moving only the focus group, as described above, it is possible to reduce the size of the drive mechanism and realize quick autofocus and the like. become.

1-3. Conditional expression Next, the conditions that the zoom lens should satisfy or the conditions that are preferable to satisfy will be described. The zoom lens adopts the above configuration and is characterized by satisfying the following conditional expression (1) and conditional expression (2).

Conditional expression (1):
−1.60 <β3rw <−0.35
Conditional expression (2):
0.75 <f1 / √ (fw x ft) <1.25

However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focal length fw of the first lens group: Focal length of the entire zoom lens system at the wide-angle end ft: Focal length of the entire zoom lens system at the telephoto end

1-3-1. Conditional expression (1)
The conditional equation (1) is an equation that defines the combined lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens. That is, it is an equation that defines the combined lateral magnification at infinity focusing at the wide-angle end of all the lenses arranged after the lens on the most object side of the third lens group. By satisfying the conditional expression (1), it is possible to secure a flange back suitable for an imaging device to which an interchangeable lens system such as a single-lens reflex camera or a mirrorless single-lens camera is applied.

On the other hand, when the numerical value of the conditional expression (1) becomes equal to or more than the upper limit value, the flange back at the wide-angle end becomes short, and it becomes difficult to secure a flange back suitable for the interchangeable lens system, which is not preferable. On the other hand, when the numerical value of the conditional expression (1) becomes equal to or less than the lower limit value, the flange back at the wide-angle end becomes larger than the flange back required for the interchangeable lens system. That is, the total optical length of the zoom lens at the wide-angle end becomes long. Therefore, it is difficult to reduce the size of the zoom lens, which is not preferable.

In order to obtain the above effect, the lower limit of the conditional expression (1) is preferably -1.50, more preferably -1.48, and even more preferably -1.45 (condition). Equation (1-1) −1.45 <β3rw <−0.35) . The upper limit of the conditional expression (1) is preferably −0.38, more preferably −0.40, still more preferably −0.45, and preferably −0.48. Is even more preferable.

1-3-2. Conditional expression (2)
In the conditional expression (2), “√ (fw × ft)” indicates the focal length of the entire zoom lens system at the intermediate focal length position of the zoom lens (hereinafter, referred to as “intermediate focal length”). The conditional expression (2) is an expression that defines the ratio between the focal length of the first lens group and the intermediate focal length of the entire zoom lens system. By satisfying the conditional expression (2), it is possible to suppress the deterioration of axial chromatic aberration at the telephoto end while shortening the optical overall length as compared with the focal length. Therefore, it is possible to realize a higher performance and smaller zoom lens in the entire variable magnification range.

On the other hand, when the numerical value of the conditional expression (2) becomes equal to or larger than the upper limit value, the focal length of the first lens group becomes longer with respect to the variable magnification range of the zoom lens, so that the total optical length becomes longer and the zoom is concerned. It is difficult to reduce the size of the lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (2) becomes less than the lower limit value, the focal length of the first lens group becomes shorter than the variable magnification range of the zoom lens, so that it becomes difficult to correct the axial chromatic aberration at the telephoto end. Become. Therefore, in order to realize a high-performance zoom lens in the entire variable magnification range, it is necessary to increase the number of lenses required for aberration correction. Therefore, it is necessary to realize both miniaturization and high performance of the zoom lens. Becomes difficult.

In order to obtain the above effect, the lower limit of the conditional expression (2) is preferably 0.80, more preferably 0.85. The upper limit of the conditional expression (2) is preferably 1.20, more preferably 1.15.

1-3-3. Conditional expression (3)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (3):
0.02 <Crfr / ft <0.11
However,
Crfr: Radius of curvature of the lens surface closest to the image in the focus group ft: Focal length of the entire zoom lens system at the telephoto end

Conditional expression (3) is an expression that defines the ratio of the radius of curvature of the lens surface closest to the image in the focus group to the focal length of the entire zoom lens system at the telephoto end. First, since the numerical range of the conditional expression (3) is positive, it is required that the value of Crfr is positive. That is, in the zoom lens, it is preferable that the lens surface on the image side in the focus group has a concave shape on the image side. Then, the image plane of the focus group on the image side is formed into a lens plane shape having a radius of curvature satisfying the conditional equation (3) with respect to the focal length of the entire zoom lens system at the telephoto end. It is possible to satisfactorily perform various aberrations such as curvature and distortion, and it is possible to realize a zoom lens with higher performance in the entire focal length.

On the other hand, when the numerical value of the conditional expression (3) becomes equal to or more than the upper limit value, that is, when the radius of curvature of the lens surface on the image side in the focus group with respect to the focal length of the entire zoom lens system at the telephoto end becomes large, the distortion is distorted. It is not preferable because it is difficult to correct the aberration. Further, when the numerical value of the conditional expression (2) becomes less than the lower limit value, that is, when the radius of curvature of the lens surface on the image side in the focus group with respect to the focal length of the entire zoom lens system at the telephoto end becomes smaller, the curvature of field is curved. It becomes difficult to correct the above, which is not preferable.

In order to obtain the above effect, the lower limit of the conditional expression (3) is more preferably 0.03, further preferably 0.04, and even more preferably 0.05. The upper limit of the conditional expression (3) is more preferably 0.10, further preferably 0.095, and even more preferably 0.09.

1-3-4. Conditional expression (4)
In the zoom lens, the focus group is composed of one lens having a negative refractive power, and it is preferable that the following conditional expression is satisfied.

Conditional expression (4):
40.0 <νdLfn
However,
νdLfn: Abbe number on the d-line of a lens having a negative refractive power that constitutes a focus group

Conditional expression (4) is an expression that defines the Abbe number with respect to the d-line of the lens having a negative refractive power when the focus group is composed of one lens having a negative refractive power. By satisfying the conditional equation (4), that is, by configuring the focus group with a negative lens having a smaller dispersion than a lens having an Abbe number of 40.0, the axial chromatic aberration and the chromatic aberration of magnification generated in the focus group are reduced. can do. Therefore, even when the focus group is composed of one negative lens, it is possible to satisfactorily correct these chromatic aberrations that are likely to occur when focusing a close subject, and it is possible to realize high optical performance in the entire focusing range. can.

In order to obtain the above effect, the lower limit of the conditional expression (4) is more preferably 42.0 and even more preferably 44.0. As the Abbe number increases, the dispersion of the lens decreases, so that chromatic aberration is less likely to occur. Therefore, from the viewpoint of reducing the chromatic aberration generated in the focus group, the larger the value of the conditional expression (4) is, the more preferable it is, and it is not necessary to set an upper limit value in particular. However, the Abbe number of the existing glass material is about 100. Further, a low-dispersion glass material having a large Abbe number is generally expensive. Therefore, from the viewpoint of cost in manufacturing the zoom lens, the upper limit of the conditional expression (4) is preferably 100, more preferably 85.0, and preferably 77.0. More preferred.

1-3-5. Conditional expression (5)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (5):
-0.25 <(Crff + Crfr) / (Crff-Crfr) <5.00
However,
Crff: Radius of curvature of the lens surface closest to the object in the focus group Crfr: Radius of curvature of the lens surface closest to the image side in the focus group

The conditional expression (5) is an expression for defining the shape of the lens surface of the lens forming the focus group. When the conditional expression (5) is satisfied, the lens forming the focus group has a shape in which the surface on the image side has a stronger curvature than the surface on the object side. By forming the focus group with a lens having a shape that satisfies the conditional expression (5), a strong negative refractive power can be arranged in the focus group, and the amount of movement of the focus group when the close subject is in focus can be reduced. .. At the same time, it is possible to suppress fluctuations in coma and curvature of field due to movement of the focus group, and to satisfactorily correct coma and curvature of field even when focusing on a close subject. Therefore, it is possible to reduce the size of the zoom lens and improve the performance in the entire focusing range, which is preferable.

In order to obtain the above effect, the lower limit of the conditional expression (5) is more preferably −0.20, further preferably −0.10, and even more preferably 0.50. The upper limit of the conditional expression (5) is more preferably 4.00, further preferably 3.00, and even more preferably 2.50.

The range of the conditional expression (5) may be satisfied as the following conditional expression (5-1) from the numerical examples (Examples 1 and 2) to which the specific numerical values of the zoom lens described below are applied. preferable.
(5-1) 0.931 ≦ (Crff + Crfr) / (Crff-Crfr) ≦ 2.074

1-3-6. Conditional expression (6)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (6):
0.39 <f1 / ft <0.70
However,
f1: Focal length of the first lens group ft: Focal length of the entire zoom lens system at the telephoto end

The conditional expression (6) is an expression that defines the ratio between the focal length of the first lens group and the focal length of the entire zoom lens system at the telephoto end. By satisfying the conditional expression (6), it becomes easy to realize a zoom lens having a larger telephoto ratio while maintaining high optical performance. That is, it becomes easier to realize a zoom lens having high performance and a short optical overall length as compared with the focal length of the entire zoom lens system at the telephoto end.

On the other hand, when the numerical value of the conditional expression (6) becomes equal to or larger than the upper limit value, that is, when the focal length of the first lens group becomes larger than the focal length of the entire zoom lens system at the telephoto end, the focal length at the telephoto end Since the total optical length of the zoom lens becomes long, it is not preferable in order to reduce the size of the zoom lens. On the other hand, when the numerical value of the conditional expression (6) becomes less than the lower limit value, that is, when the focal length of the first lens group becomes smaller than the focal length of the entire zoom lens system at the telephoto end, axial chromatic aberration at the telephoto end It becomes difficult to correct chromatic aberration and spherical aberration, and it becomes difficult to realize a high-performance zoom lens in the entire variable focal length range.

In order to obtain the above effect, the lower limit of the conditional expression (6) is more preferably 0.40, further preferably 0.41, further preferably 0.44, and 0.46. Is even more preferable. The upper limit of the conditional expression (6) is more preferably 0.68, further preferably 0.65, and even more preferably 0.62.

1-3-7. Conditional expression (7)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (7):
-15.0 << {1- (βft × βft)} × βftr × βftr <−5.5
However,
βft: Lateral Magnification at Infinity Focus at the Telephoto End of the Focus Group βftr: Composite Magnification at Infinity Focus at the Telephoto End of All Lens Groups Placed on the Image Side of the Focus Group

The conditional expression (7) is an expression that defines the focus sensitivity of the focus group, that is, the amount of image plane movement when the focus group moves by a unit amount. By satisfying the conditional expression (7), the amount of movement of the focus group at the time of focusing from an infinity object to a nearby object can be set within an appropriate range, quick autofocus can be realized, and the zoom can be achieved. It becomes easier to reduce the size of the lens.

On the other hand, when the numerical value of the conditional expression (7) exceeds the upper limit value, that is, when the focus sensitivity of the focus group becomes too small, the amount of movement of the focus group when focusing from an infinity object to a nearby object This is not preferable because the total optical length of the zoom lens becomes long and it becomes difficult to realize quick autofocus. On the other hand, when the numerical value of the conditional expression (7) becomes less than the lower limit value, that is, when the focus sensitivity of the focus group becomes too large, it is necessary to control the position of the focus group with high accuracy in order to adjust the focusing position. , It is not preferable because it becomes difficult to control the focus group.

In order to obtain the above effect, the lower limit of the conditional expression (7) is more preferably -14.5, further preferably -14.0, and even more preferably -13.5. It is even more preferably -13.0 and even more preferably -12.5. The upper limit of the conditional expression (7) is more preferably -6.0, further preferably -6.5, further preferably -7.0, and -8.0. It is even more preferable to have.

1-3-8. Conditional expression (8)
When the zoom lens is configured so that the first lens group moves toward the object when the magnification is changed from the wide-angle end to the telephoto end, it is preferable that the following conditional expression is satisfied.

Conditional expression (8):
0.10 << | X1 | / ft <0.26
However,
X1: The amount by which the first lens group moves toward the object when the magnification is changed from the wide-angle end to the telephoto end.

The conditional expression (8) is an expression that defines the amount of movement of the first lens group when the first lens group is configured to move toward the object when the magnification is changed from the wide-angle end to the telephoto end. By satisfying the conditional expression (8), the amount of movement of the first lens group at the time of the above scaling is within an appropriate range, and a better power arrangement can be performed for each lens group. Therefore, various aberrations such as axial chromatic aberration and spherical aberration can be satisfactorily corrected with a smaller number of lenses, and it becomes easier to realize a high-performance zoom lens in the entire focusing region. At the same time, the zoom lens can be further miniaturized. Further, since the amount of movement of the focus group at the time of focusing can be set within an appropriate range, quick autofocus can be realized and drive control of the focus group can be appropriately performed.

On the other hand, when the numerical value of the conditional expression (8) becomes equal to or more than the upper limit value, the amount of movement of the first lens group at the time of scaling from the wide-angle end to the telescopic end becomes large. That is, since it is necessary to make the lens barrel length in the telephoto end state longer than the lens barrel length in the wide-angle end state, the lens barrel structure such as the nesting structure and the cam structure of the lens barrel becomes complicated. As a result, the lens barrel becomes large, and it becomes difficult to reduce the size and weight of the entire lens unit. On the other hand, when the numerical value of the conditional expression (8) becomes equal to or less than the lower limit value, the amount of movement of the first lens group at the time of scaling from the wide-angle end to the telephoto end becomes small. In this case, in order to realize a zoom lens having a large magnification ratio, it is necessary to increase the power distributed to other lens groups. Therefore, in order to realize a high-performance zoom lens, it is necessary to increase the number of lenses in order to correct various aberrations such as axial chromatic aberration and spherical aberration, and it is possible to reduce the size and weight of the zoom lens. It becomes difficult.

In order to obtain the above effect, the lower limit of the conditional expression (8) is more preferably 0.12, further preferably 0.14, and even more preferably 0.16. Further, the upper limit of the conditional expression (8) is more preferably 0.25.

1-3-9. Conditional expression (9)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (9):
1.40 <f1 / fw <3.20
However,
f1: Focal length of the first lens group fw: Focal length of the entire zoom lens system at the wide-angle end

The conditional equation (9) is an equation that defines the ratio between the focal length of the first lens group and the focal length of the entire zoom lens system at the wide-angle end. By satisfying the conditional equation (9), the focal length of the first lens group with respect to the focal length of the entire zoom lens system at the wide-angle end becomes within a more appropriate range, and the optical performance of the zoom lens at the wide-angle end is further improved. This is preferable in terms of miniaturization.

On the other hand, when the numerical value of the conditional expression (9) becomes equal to or larger than the upper limit value, the focal length of the first lens group becomes longer than the focal length at the wide-angle end of the zoom lens, and the zoom lens and the lens at the wide-angle end. It is not preferable for reducing the size of the unit. On the other hand, when the numerical value of the conditional expression (9) becomes less than the lower limit value, the focal length of the first lens group becomes shorter than the focal length at the wide-angle end of the zoom lens, and coma aberration and distortion are corrected at the wide-angle end. It will be difficult. Therefore, in order to realize a high-performance zoom lens in the entire variable magnification range, it is necessary to increase the number of lenses required for aberration correction. Therefore, it is necessary to realize both miniaturization and high performance of the zoom lens. Becomes difficult.

In order to obtain the above effect, the lower limit of the conditional expression (9) is more preferably 1.50 and even more preferably 1.60 (conditional expression (9-1) 1.60 <f1 /. fw <3.20) It is more preferable that it is 1.70. The upper limit of the conditional expression (9) is more preferably 3.00, further preferably 2.80, further preferably 2.60, and more preferably 2.30. More preferred.

1-3-10. Conditional expression (10)
In the zoom lens, the first lens group preferably includes at least two lenses having a positive refractive power, and satisfies the following conditional expression.

Conditional expression (10):
64.0 <νd1pave <83.0
However,
νd1pave: Average value of Abbe numbers in the d-line of all lenses having a positive refractive power included in the first lens group

The conditional equation (10) is an equation that defines the average value of the Abbe numbers in the d-line of all the lenses having a positive refractive power included in the first lens group. As described above, since a glass material having a large Abbe number has a low dispersion, the occurrence of chromatic aberration can be suppressed by using a lens made of a glass material having a large Abbe number. However, a glass material having a large Abbe number is generally expensive. Therefore, by satisfying the conditional expression (10), it is possible to satisfactorily correct the axial chromatic aberration at the telephoto end and suppress the cost increase of the zoom lens.

On the other hand, when the numerical value of the conditional expression (10) becomes equal to or more than the upper limit value, that is, when the average Abbe number of the lenses having a positive refractive power included in the first lens group becomes large, the first lens group is formed. The lens having a positive refractive power used for this purpose becomes expensive, which is not preferable from the viewpoint of cost in manufacturing the zoom lens. On the other hand, when the numerical value of the conditional expression (10) is equal to or less than the lower limit value, the Abbe number of all the lenses having a positive refractive power included in the first lens group is small and the dispersion is large, so that axial chromatic aberration at the telephoto end is caused. It becomes difficult to correct, and it becomes difficult to realize a high-performance zoom lens in the entire variable magnification range.

In order to obtain the above effect, the lower limit of the conditional expression (10) is more preferably 65.3, further preferably 66.2, and even more preferably 67.1. The upper limit of the conditional expression (10) is more preferably 82.0, further preferably 80.5, further preferably 79.0, and more preferably 77.0. Even more preferably, it is even more preferably 73.0.

1-3-11. Conditional expression (11)
The zoom lens preferably satisfies the following conditional expression.

Conditional expression (11):
0.86 << | β2t | <20.00
However,
β2t: Lateral magnification at infinity in focus at the telephoto end of the second lens group

The conditional expression (11) is an expression that defines the lateral magnification at infinity focusing at the telephoto end of the second lens group. By satisfying the conditional equation (11), the lateral magnification of the second lens group at the telephoto end infinity focusing becomes within a more appropriate range, and the magnification action of the second lens group causes the zoom lens to change. It becomes easier to realize a high-performance zoom lens in the entire variable magnification range while increasing the magnification ratio.

On the other hand, when the numerical value of the conditional expression (11) becomes equal to or larger than the upper limit value, the lateral magnification at the telephoto end of the second lens group at the time of infinity focusing becomes large, and the scaling effect of the second lens group at the telephoto end increases. Becomes too large. Therefore, it becomes difficult to correct various aberrations such as spherical aberration, curvature of field, and coma, and it becomes difficult to construct a high-performance zoom lens with a small number of lenses, and it is difficult to reduce the size of the zoom lens. become. On the other hand, when the numerical value of the conditional expression (11) is equal to or less than the lower limit value, the lateral magnification of the second lens group at the time of focusing at the telephoto end is small, and the scaling effect of the second lens group at the telephoto end becomes too small. Therefore, in order to obtain a telescopic zoom lens having a long focal length at the telephoto end, it is necessary to lengthen the focal length of the first lens group, and the total optical length of the zoom lens becomes long. Therefore, the zoom lens and the lens unit It becomes difficult to reduce the size of the lens.

In order to obtain the above effect, the lower limit of the conditional expression (11) is more preferably 0.90, further preferably 0.95, further preferably 1.00, and 1.05. Is even more preferable. The upper limit of the conditional expression (11) is more preferably 18.0, further preferably 16.0, and even more preferably 15.0.

1-3-12. Conditional expression (12)
It is preferable that the zoom lens satisfies the following conditional expression.

Conditional expression (12):
1.10 <Bfw / (fw x tanωw) <3.50
However,
Bfw: Air equivalent length from the most image-side surface to the image plane at the wide-angle end of the zoom lens ωw: Half angle of view of the most off-axis main ray at the wide-angle end of the zoom lens

The conditional expression (12) is an expression for defining the length of the flange back at the wide-angle end of the zoom lens. By satisfying the conditional expression (12), the flange back at the wide-angle end of the zoom lens can be made to a length suitable for an imaging device to which a lens exchange system is applied.

On the other hand, if the numerical value of the conditional expression (12) is equal to or larger than the upper limit value, the flange back at the wide-angle end of the zoom lens becomes too long, which is not preferable in order to reduce the size of the zoom lens. On the other hand, if the numerical value of the conditional expression (12) is not more than the lower limit value, the flange back at the wide-angle end of the zoom lens becomes short, so that the zoom lens is required for the interchangeable lens of the imaging device to which the lens interchangeable system is applied. It is not preferable because it becomes difficult to secure the flange back.

In order to obtain the above effect, the lower limit of the conditional expression (12) is more preferably 1.15, further preferably 1.20, and even more preferably 1.40. Is even more preferable. The upper limit of the conditional expression (12) is more preferably 3.20, further preferably 3.00, and even more preferably 2.90.

It is also preferable that the range of the conditional expression (12) is satisfied as the following conditional expression (12-1) from the above-mentioned more preferable numerical values.
(12-1) 1.80 <Bfw / (fw × tanωw) <3.00

1-3-13. Conditional expression (13)
It is preferable that the zoom lens satisfies the following conditional expression.

Conditional expression (13):
−0.30 <fF / ft <−0.05
However,
fF: Focal length of the focus group

The conditional expression (13) is an expression that defines the ratio between the focal length of the focus group and the focal length of the entire zoom lens system at the telephoto end. By satisfying the conditional equation (13), the focal length of the focus group with respect to the focal length of the entire zoom lens system at the telephoto end is within an appropriate range, and correction of various aberrations such as axial chromatic aberration and spherical aberration is lessened. This can be done satisfactorily with the number of lenses, and it becomes easier to realize a high-performance zoom lens over the entire focal length. At the same time, the zoom lens can be further miniaturized. Further, since the amount of movement of the focus group at the time of focusing can be set within an appropriate range, quick autofocus can be realized and the position control of the focus group can be appropriately performed.

On the other hand, when the numerical value of the conditional expression (13) becomes equal to or more than the upper limit value, the focal length of the focus group with respect to the focal length of the entire zoom lens system at the telephoto end becomes too short. Therefore, it becomes difficult to correct various aberrations such as axial chromatic aberration, spherical aberration, and curvature of field when focusing on a close subject, and it is possible to realize a high-performance zoom lens in the entire focusing range with a small number of lenses. Becomes difficult. Further, in this case, since the focus sensitivity of the focus group becomes large, it is necessary to control the position of the focus group with high accuracy in order to adjust the focusing position, which makes it difficult to control the position of the focus group, which is not preferable. ..

On the other hand, when the numerical value of the conditional expression (13) becomes equal to or less than the lower limit value, the focal length of the focus group becomes too long with respect to the focal length of the entire zoom lens system at the telephoto end. In this case, since the focus sensitivity of the focus group becomes small, the amount of movement of the focus group at the time of focusing becomes large, the total optical length of the zoom lens becomes long, and it becomes difficult to realize quick autofocus. Therefore, it is not preferable.

In order to obtain the above effect, the lower limit of the conditional expression (13) is more preferably −0.25, further preferably −0.20, and even more preferably −0.18. The upper limit of the conditional expression (13) is more preferably −0.07, further preferably −0.09, and even more preferably −0.10.

1-3-14. Conditional expression (14) and conditional expression (15)
When the lens N of the zoom lens has a negative refractive power and satisfies the following conditional expression, it is preferable that at least one lens N is included in the third lens group and thereafter.

(14) 15.0 <νdN <42.0
(15) 1.85 <NdN <2.15
However,
νdN: Abbe number on the d-line of the lens N NdN: Refractive index on the d-line of the lens N

When at least one of the lenses having a negative refractive power included in the third lens group and thereafter is a lens N having a high dispersion and a high refractive power that satisfies the above conditional equation (14) and the conditional equation (15), the first lens is used. Since the chromatic aberration generated in the lens having a positive refractive power constituting the lens group can be canceled by the lens N, the axial chromatic aberration at the telephoto end can be reduced. Therefore, the axial chromatic aberration at the telephoto end can be reduced without using an expensive glass material having extremely small dispersion as the glass material of the lens having a positive refractive power constituting the first lens group. Therefore, it is preferable because it is possible to suppress the cost increase while realizing a high-performance zoom lens.

In order to obtain the above effect, the lower limit of the conditional expression (14) is more preferably 20.0, further preferably 24.0, further preferably 25.2, and 28.0. Is even more preferable. The upper limit of the conditional expression (14) is more preferably 41.0, further preferably 39.0, and even more preferably 37.5.

Further, in order to obtain the above effect, the lower limit value of the conditional expression (15) is more preferably 1.87, and further preferably 1.89. The upper limit of the conditional expression (12) is more preferably 2.05, further preferably 1.98, and even more preferably 1.95.

By including the lens N in the third lens group in the zoom lens, the chromatic aberration generated in the first lens group in the third lens group can be offset, so that the axial chromatic aberration at the telephoto end is further reduced. Can be preferred. The zoom lens may include a plurality of lenses N having a negative refractive power satisfying the conditional expression (14) and the conditional expression (15) in the third lens group and thereafter.

2. Imaging Device Next, the imaging device of the present embodiment will be described. The image pickup device of the present embodiment is characterized by including the zoom lens and an image pickup element provided on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal. And.

In the present invention, the image sensor or the like is not particularly limited, and a solid-state image sensor such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used.

In particular, the zoom lens can secure a flange back suitable for an interchangeable lens system such as a single-lens reflex camera or a mirrorless single-lens camera even at a wide-angle end. Therefore, the image pickup device is suitable for an image pickup device to which these interchangeable lens systems are applied.

The image pickup apparatus has an image processing unit that electrically processes an optical image (image data) converted into an electrical signal by the image pickup element, and the image processing unit performs image processing on the image data. It is preferable that it is configured so that it can be applied. For example, in the image processing unit, the optical image obtained when the subject is imaged using the zoom lens is distorted (ideal) due to various aberrations of the zoom lens with respect to the ideal subject image. There may be a deviation from the subject image). Therefore, based on the aberration characteristics of the zoom lens, data for supplementary image correction for correcting these aberrations is prepared in advance, and the image data is used by the image processing unit by the image processing unit. By electrically processing the image data, it is possible to generate image data in which the distortion of the optical image is corrected. The image pickup apparatus may have a distortion correction data storage unit in which the image correction data is stored in advance, or may have a data storage unit configured to store the image correction data. You may. Further, the imaging device includes a communication means such as a wireless communication means and a data acquisition unit for acquiring image correction data stored in an external device via the communication means or the like, and via the communication means or the like. The image data may be electrically processed by the image processing unit using the image correction data acquired in the above. These specific aspects of image processing are not particularly limited. The ideal subject image refers to an optical image obtained when a subject is imaged using a lens (zoom lens) having no aberration.

The imaging device is provided with the image processing unit, and for example, distortion of an optical image caused by distortion can be corrected by the image processing unit using data for distortion correction prepared in advance. When it is configured, it is preferable that the negative refractive force arranged on the image side of the aperture can be strengthened in the zoom lens, and the optical total length and the radial direction of the zoom lens can be reduced.

Further, the image pickup apparatus is provided with the image processing unit, and for example, the distortion of the optical image caused by the chromatic aberration of magnification is corrected by the image processing unit using the data for correcting the chromatic aberration of magnification prepared in advance. When it is configured to be possible, in the zoom lens, the negative refractive force arranged on the image side of the aperture can be strengthened, and the optical total length and the radial direction of the zoom lens can be reduced. preferable.

Next, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the following examples. The zoom lens of each of the following examples is a zoom lens (variable magnification optical system) used in the above-mentioned imaging device (optical device), and can be particularly preferably applied to an imaging device to which an interchangeable lens imaging system is applied. .. Further, in each lens cross-sectional view, the left side is the object side and the right side is the image side when viewed from the drawing.

(1) Configuration of Optical System FIG. 1 is a cross-sectional view showing a lens configuration at infinity focusing at the wide-angle end of the zoom lens of Example 1 according to the present invention. The zoom lens has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. It is composed of a fourth lens group G4 having a refractive power of, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a negative refractive power. The fifth lens group G5 is a focus group and is composed of one lens, which will be described later. When focusing from an infinity object to a short-distance object, the fifth lens group G5 moves toward the image side along the optical axis. The aperture diaphragm S is arranged on the most image plane side of the third lens group G3. In FIG. 1, "CG" refers to a cover glass, a low-pass filter, an infrared filter, and the like. “IMG” is an image plane, and indicates an image pickup surface of a solid-state image sensor such as a CCD sensor or a CMOS sensor, a film surface of a silver salt film, or the like. Since these points are the same in the cross-sectional views of the lenses shown in the other examples, the description thereof will be omitted below.

Next, the configuration of each lens group will be described. The first lens group G1 is composed of a bonded lens in which a negative meniscus lens L1 having a convex shape on the object side and a biconvex lens L2 are joined in order from the object side, and a biconvex lens L3.

The second lens group G2 is composed of a junction lens in which a biconcave lens L4 and a positive meniscus lens L5 having a convex shape on the object side are joined in order from the object side, and a biconcave lens L6.

The third lens group G3 is a junction in which a biconvex lens L7, a biconvex lens L8 and a biconcave lens L9 are joined, and a biconcave lens L10 and a positive meniscus lens L11 having a convex shape on the object side are joined in this order from the object side. It is composed of a lens and an aperture diaphragm S.

The fourth lens group G4 is composed of a biconvex lens L12, a biconvex lens L13, and a junction lens to which a negative meniscus lens L14 having a concave object side is joined in order from the object side.

The fifth lens group G5 is composed of a negative meniscus lens L15 having a convex shape on the object side.

The sixth lens group G6 is composed of a bonded lens in which a biconcave lens L16 and a biconvex lens L17 are joined.

In the zoom lens of the first embodiment, the locus of movement of each lens group at the time of scaling from the wide-angle end to the telephoto end is as shown in FIG. 1, the first lens group moves to the object side, and the second lens The group is fixed, the third lens group moves to the object side, the fourth lens group moves to the object side, the fifth lens group moves to the object side, and the sixth lens group also moves to the object side. Here, the loci of movement (direction of movement and amount of movement) of the fourth lens group and the sixth lens group at the time of magnification change are the same. The amount of movement of the 4th lens group and the 6th lens group at the time of variable magnification and the amount of movement of the 5th lens group are slightly different.

Here, as a modification, for example, when the fourth lens group to the sixth lens group are configured as one lens group and all of these lens groups are moved in the same locus at the time of magnification change, the zoom lens of the first embodiment is also used. It is possible to obtain optical performance substantially equivalent to that of the present invention, which is within the scope of the present invention. In this case, this lens group includes a fourth lens group as the object side partial lens group, a focus group (fifth lens group) as the partial lens group, and a sixth lens group as the image side partial lens group in order from the object side. It will be.

Further, as another modification, for example, when the third lens group to the sixth lens group are configured as one lens group and all of these lens groups are moved in the same locus at the time of magnification change, the zoom of the first embodiment is also performed. It is possible to obtain optical performance substantially equivalent to that of a lens, which is within the scope of the present invention. In this case, in this lens group, the third lens group and the fourth lens group as the object side partial lens group, the focus group (fifth lens group) as the partial lens group, and the image side partial lens group are the third in order from the object side. It will be equipped with 6 lens groups.

Further, the zoom lens of the first embodiment can be used, for example, by eccentricizing at least one lens constituting the zoom lens of the first embodiment when image blurring occurs during shooting due to camera shake or the like. By moving the lens in orthogonal directions, it is possible to provide a group of anti-vibration lenses that correct image blur. For example, image stabilization on the image plane IMG can be performed by moving the junction lens to which the biconcave lens L10 included in the third lens group G3 and the positive meniscus lens L11 having a convex shape on the object side are joined in a direction perpendicular to the optical axis. It can be a group of anti-vibration lenses to be performed.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 1 shows the surface data of the optical system. In Table 1, "plane number" is the order of the lens surfaces counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the distance on the optical axis of the lens surface, and "Nd" is the d line. The refractive index with respect to (wavelength λ = 587.56 nm), “vd” indicates the Abbe number with respect to the d line, and “H” indicates the effective radius. Further, "S" attached to the next column of "surface number" indicates an aperture stop. Further, "INF" described in the column of "r" means "∞ (infinity)". The unit of length in each table is "mm", and the unit of angle of view is "°".

Table 2 shows the specification data of the zoom lens. Table 2 shows the focal length (f), F number (Fno), half angle of view (ω), image height (Y), and total optical length (TL) of the zoom lens at the wide-angle end, the intermediate focal length position, and the telephoto end. Is shown.

Table 3 shows the variable intervals on the optical axis at the time of scaling (however, at the time of focusing at infinity). In Table 3, the intervals between the lens surfaces at the wide-angle end, the intermediate focal length position, and the telephoto end are shown in order from the left side.

Table 4 shows the variable intervals on the optical axis when a close subject (shooting distance: 3.00 m) is in focus. In Table 4, the intervals between the lens surfaces at the wide-angle end, the intermediate focal length position, and the telephoto end are shown in order from the left side. Further, Table 5 shows the focal lengths of each lens group. In Table 5, the “plane number” means the number of the lens plane included in each lens group.

Further, Table 17 shows the numerical values of the above conditional expressions (1) to (15) of the optical system. Since the matters concerning each of these tables are the same in each of the tables shown in other examples, the description thereof will be omitted below.

Further, FIG. 2 shows a longitudinal aberration diagram at infinity focusing at the wide-angle end of the zoom lens. Spherical aberration, astigmatism, and distortion are in order from the left side of the drawing.

In the figure showing spherical aberration, the vertical axis is the ratio to the open F number (indicated by FNO in the figure), the horizontal axis is defocused, the solid line is the d line (wavelength 587.56 nm), and the single point chain line is the g line (wavelength). 435.84nm), the broken line represents the spherical aberration at the C line (wavelength 656.27nm).

In the figure showing astigmatism, the vertical axis represents the half angle of view (ω), the horizontal axis is defocused, the solid line is the sagittal image plane (S) with respect to the d line (wavelength 587.56 nm), and the dotted line is with respect to the d line. It represents astigmatism in the meridional image plane (T).

In the diagram showing the distortion, the vertical axis represents the half angle of view (ω) and the horizontal axis represents%, which represents the distortion at the d line (wavelength 587.56 nm).

The back focus "fb" at the infinity focusing at the wide-angle end of the zoom lens is as follows. However, the following values do not include the cover glass (Nd = 1.5168) having a thickness of 2.5 mm, and the same applies to the back focus shown in other examples.

fb = 44.319 (mm)

Further, FIG. 3 shows a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the intermediate focal length position of the zoom lens, and FIG. 4 shows an infinity focusing diagram at the telephoto end of the zoom lens. The spherical aberration diagram, the astigmatism diagram, and the distortion diagram of the above are shown. The matters related to the aberration diagram described in FIG. 2 are the same in FIGS. 3 and 4, and are also the same in each of the diagrams shown in other examples. Therefore, the description thereof will be omitted below.

(1) Configuration of Optical System FIG. 5 is a cross-sectional view showing a lens configuration at infinity focusing at the wide-angle end of the zoom lens of the second embodiment according to the present invention. The zoom lens has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. It is composed of a fourth lens group G4 having a refractive power of, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power. The fifth lens group is a focus group, and is composed of one lens, which will be described later. When focusing from an infinity object to a short-distance object, the fifth lens group G5 moves toward the image side along the optical axis. The aperture diaphragm S is arranged on the most image plane side of the third lens group G3.

Next, the configuration of each lens group will be described. The first lens group G1 is composed of a bonded lens in which a negative meniscus lens L1 having a convex shape on the object side and a biconvex lens L2 are joined in order from the object side, and a positive meniscus lens L3 having a convex shape on the object side.

The second lens group G2 is composed of a negative meniscus lens L4 having a convex shape on the object side, a junction lens to which a biconcave lens L5 and a positive meniscus lens L6 having a convex shape on the object side are joined in this order from the object side.

The third lens group G3 is composed of a biconvex lens L7, a biconcave lens L8, a biconvex lens L9, and an aperture diaphragm S in order from the object side.

In the fourth lens group G4, in order from the object side, a junction lens to which the object side convex negative meniscus lens L10 and the biconvex lens L11 are bonded, and a biconvex lens L12 and the object side concave negative meniscus lens L13 are bonded. It is composed of a junction lens and a biconvex lens L14.

The fifth lens group G5 is composed of a biconcave lens L15 whose both sides are aspherical.

The sixth lens group G6 is composed of a bonded lens in which a positive meniscus lens L16 having a concave shape on the object side and a biconcave lens L17 are bonded, and a biconvex lens L18.

In the zoom lens of the second embodiment, the locus of movement of each lens group at the time of scaling from the wide-angle end to the telephoto end is as shown in FIG. 5, the first lens group moves to the object side, and the second lens The group moves to the image side, the third lens group moves to the object side, the fourth lens group moves to the object side, the fifth lens group moves to the object side, and the sixth lens group also moves to the object side. After that, move to the image side. In the zoom lens of Example 2, all the lens groups are movable groups, but the amount of movement of the sixth lens group is small. Therefore, even if the sixth lens group arranged on the image side is set as the fixed group, the same optical performance as the zoom lens of the second embodiment can be obtained, which is within the scope of the present invention.

Further, also in the zoom lens of the second embodiment, when image blurring occurs during shooting due to camera shake or the like, at least one lens constituting the zoom lens of the second embodiment is eccentric, for example, an optical axis. By moving the lens in a direction orthogonal to the image blur, a group of anti-vibration lenses for correcting image blur can be provided. For example, by moving the second lens group G2 in a direction perpendicular to the optical axis, it is possible to obtain an anti-vibration lens group that corrects image blur on the image plane IMG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 6 shows the surface data of the zoom lens, Table 7 shows the specification data, Table 8 shows the variable interval on the optical axis at the time of scaling, and Table 9 shows the variable interval on the optical axis at the time of focusing (however). , Shooting distance 0.70 m), Table 10 shows the focal length of each lens group, and Table 17 shows the numerical values of the above-mentioned conditional expressions (1) to (15) of the zoom lens.

In Table 6, "ASP" attached to the column next to the surface number indicates that the lens surface is an aspherical surface, and the aspherical surface data is shown in Table 11. In Table 11, the aspherical data shows the aspherical coefficient when the aspherical shape is defined by the following equation. However, in the table, " ^Ea " indicates "x10-a". The aspherical surface data shows the aspherical coefficient when the aspherical surface is defined by the following formula, and the aspherical coefficient of each order.

However, in the above equation, "x" is the amount of displacement from the reference plane in the optical axis direction (the image plane side is positive), "r" is the radius of curvature of the near axis, and "H" is the direction perpendicular to the optical axis. The height from the optical axis, "k" is the curvature of curvature, and "An" is the nth-order aspherical coefficient (where n = 4, 6, 8, 10).

Further, FIG. 6 is a longitudinal aberration diagram at infinity focusing at the wide-angle end of the zoom lens, FIG. 7 is a longitudinal aberration diagram at infinity focusing at the intermediate focal position, and FIG. 8 is an infinity focusing diagram at the telephoto end. The longitudinal aberration diagram of time is shown.

The back focus "fb" at the infinity focusing at the wide-angle end of the zoom lens is as follows.
fb = 54.863 (mm)

(1) Configuration of Optical System FIG. 9 is a cross-sectional view showing a lens configuration at infinity focusing at the wide-angle end of the zoom lens of Example 3 according to the present invention. The zoom lens includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. It is composed of a fourth lens group G4 having a refractive power of the above and a fifth lens group G5 having a negative refractive power. The fourth lens group G4 is a focus group and is composed of one lens. When focusing from an infinity object to a short-distance object, the fourth lens group G4 moves toward the image side along the optical axis. The aperture diaphragm S is arranged in the third lens group G3.

The first lens group G1 is composed of a bonded lens in which a negative meniscus lens L1 having a convex shape on the object side and a biconvex lens L2 are joined in order from the object side, and a biconvex lens L3.

The second lens group G2 is a junction in which a positive meniscus lens L4 having a convex shape on the image side and a biconcave lens L5 are joined, a biconcave lens L6, a biconcave lens L7, and a biconvex lens L8 are joined in order from the object side. It consists of a lens.

The third lens group G3 includes a junction lens in which a biconvex lens L9 and a concave negative meniscus lens L10 on the object side are joined, a biconvex lens L11, an aperture diaphragm S, a biconcave lens L12, and a biconvex lens L13 in order from the object side. It is composed of a bonded lens in which a biconvex lens L14 and a biconcave lens L15 are joined, and a positive meniscus lens L16 having a convex shape on the object side.

The fourth lens group G4 is composed of a negative meniscus lens L17 having a convex shape on the object side.

The fifth lens group G5 is composed of a positive meniscus lens L18 having a concave shape on the object side and a biconcave lens L19.

In the zoom lens of the third embodiment, the locus of movement of each lens group at the time of scaling from the wide-angle end to the telephoto end is as shown in FIG. 9, the first lens group moves to the object side, and the second lens The group moves to the image side and then to the object side, the third lens group moves to the object side, the fourth lens group moves to the object side, and the fifth lens group is fixed.

Further, also in the zoom lens of the third embodiment, when image blurring occurs during shooting due to camera shake or the like, at least one lens constituting the zoom lens of the third embodiment is eccentric, for example, an optical axis. By moving the lens in a direction orthogonal to the image blur, a group of anti-vibration lenses for correcting image blur can be provided. For example, by moving the three lenses of the biconcave lens L6 included in the second lens group G2 and the junction lens to which the biconcave lens L7 and the biconvex lens L8 are joined in a direction perpendicular to the optical axis, the image plane IMG. It can be a group of anti-vibration lenses that corrects image blur.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 12 shows the surface data of the zoom lens, Table 13 shows the specification data, Table 14 shows the variable interval on the optical axis at the time of scaling, and Table 15 shows the variable interval on the optical axis at the time of focusing (however). , Shooting distance 1.50 m), Table 16 shows the focal length of each lens group, and Table 17 shows the numerical values of the above-mentioned conditional expressions (1) to (15) of the zoom lens.

Further, FIG. 10 shows a longitudinal aberration diagram at infinity focusing at the wide-angle end of the zoom lens, FIG. 11 shows a longitudinal aberration diagram at infinity focusing at the intermediate focal position, and FIG. 12 shows an infinity focusing diagram at the telephoto end. The longitudinal aberration diagram of time is shown.

The back focus "fb" at the infinity focusing at the wide-angle end of the zoom lens is as follows.
fb = 51.319 (mm)

According to the present invention, it is possible to provide a telephoto zoom lens and an imaging device capable of reducing the weight of the focus group while maintaining high optical performance and securing a flange back suitable for an interchangeable lens. can.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group F Focus group S Aperture

Claims (21)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are provided in this order from the object side, and the air spacing between the lens groups is provided. It is a zoom lens that changes the magnification by changing
A focus group composed of one lens is provided after the third lens group.
The focus group is composed of a single lens having a negative refractive power.
When focusing from an infinity object to a nearby object, only the focus group concerned shall be moved along the optical axis direction.
A zoom lens characterized by satisfying the following conditional expression.
(1) −1.60 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(6) 0.39 <f1 / ft <0.70
(12-1) 1.80 <Bfw / (fw × tanωw) <3.00
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focus distance of the first lens group fw: Focal distance of the entire zoom lens system at the wide-angle end ft: Focal distance of the entire zoom lens system at the telephoto end Bfw: Air equivalent length from the most image-side surface to the image surface at the wide-angle end of the zoom lens ωw: The zoom Half angle of view of the most off-axis main ray at the wide-angle end of the lens A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are provided in this order from the object side, and the air spacing between the lens groups is provided. It is a zoom lens that changes the magnification by changing
A focus group composed of one lens is provided after the third lens group.
The focus group has a convex shape on the side surface of the object.
When focusing from an infinity object to a nearby object, only the focus group concerned shall be moved along the optical axis direction.
When the magnification is changed from the wide-angle end to the telephoto end, the first lens group moves to the object side, and the lens group moves to the object side.
A zoom lens characterized by satisfying the following conditional expression.
(1-1) −1.45 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(6-1) 0.481 ≤ f1 / ft <0.70
(9-1) 1.60 <f1 / fw <3.20
(13) −0.30 <fF / ft <−0.05
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focal length of the first lens group fw: Focal length of the entire zoom lens system at the wide-angle end ft: Focal length of the entire zoom lens system at the telephoto end fF: Focal length of the focus group A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are provided in this order from the object side, and the air spacing between the lens groups is provided. It is a zoom lens that changes the magnification by changing
A focus group composed of one lens is provided after the third lens group.
When focusing from an infinity object to a nearby object, only the focus group concerned shall be moved along the optical axis direction.
A zoom lens characterized by satisfying the following conditional expression.
(1) −1.60 <β3rw <−0.35
(2) 0.75 <f1 / √ (fw x ft) <1.25
(5-1) 0.931 ≦ (Crff + Crfr) / (Crff-Crfr) ≦ 2.074
(12) 1.10 <Bfw / (fw × tanωw) <3.50
However,
β3rw: Synthetic lateral magnification at infinity focusing at the wide-angle end from the lens on the most object side of the third lens group to the lens on the image side of the zoom lens f1: Focus distance of the first lens group fw: Focal distance of the entire zoom lens system at the wide-angle end ft: Focal distance of the entire zoom lens system at the telephoto end Crff: Radius of curvature of the lens surface on the most object side in the focus group Crfr: Lens on the image side most in the focus group Radius of curvature of the surface Bfw: Air equivalent length from the most image-side surface to the image surface at the wide-angle end of the zoom lens ωw: Semi-angle of the most off-axis main ray at the wide-angle end of the zoom lens The zoom lens according to any one of claims 1 to 3, which satisfies the following conditional expression.
(3) 0.02 <Crfr / ft <0.11
However,
Crfr: Radius of curvature of the lens surface closest to the image in the focus group The focus group is composed of a single lens having a negative refractive power.
The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
(4) 55.46 ≤ νdLfn
However,
νdLfn: Abbe number on the d-line of a lens having a negative refractive power that constitutes the focus group. The zoom lens according to any one of claims 1 to 5, wherein the focus group is arranged on the image side of a lens group having a positive refractive power or a partial lens group via an air gap. The zoom lens according to claim 1 or 2, which satisfies the following conditional expression.
(5) -0.25 <(Crff + Crfr) / (Crff-Crfr) <5.00
However,
Crff: Radius of curvature of the lens surface closest to the object in the focus group Crfr: Radius of curvature of the lens surface closest to the image side in the focus group The zoom lens according to claim 3 , which satisfies the following conditional expression.
(6) 0.39 <f1 / ft <0.70 The zoom lens according to any one of claims 1 to 8, which satisfies the following conditional expression.
(7) -15.0 << {1- (βft × βft)} × βftr × βftr <-5.5
However,
βft: Horizontal magnification at infinity focusing at the telephoto end of the focus group βftr: Composite lateral magnification at infinity focusing at the telephoto end of all lens groups arranged on the image side of the focus group The zoom lens according to claim 1 or 3, wherein the first lens group moves toward an object when the magnification is changed from the wide-angle end to the telephoto end. The zoom lens according to claim 10, which satisfies the following conditional expression.
(8) 0.10 << | X1 | / ft <0.26
However,
X1: The amount by which the first lens group moves toward the object when the magnification is changed from the wide-angle end to the telephoto end. When the lens group arranged on the image side of the zoom lens is the final lens group,
The zoom lens according to any one of claims 1 to 11, wherein the focus group is a lens group other than the final lens group. The zoom lens according to claim 1 or 3, which satisfies the following conditional expression.
(9) 1.40 <f1 / fw <3.20 The first lens group includes at least two lenses having a positive refractive power.
The zoom lens according to any one of claims 1 to 13, which satisfies the following conditional expression.
(10) 64.0 <νd1pave <83.0
However,
νd1pave: The average value of the Abbe numbers on the d-line of all lenses having a positive refractive power included in the first lens group. The zoom lens according to any one of claims 1 to 14, which satisfies the following conditional expression.
(11) 0.86 << | β2t | <20.00
However,
β2t: Lateral magnification at infinity focusing at the telephoto end of the second lens group The zoom lens according to claim 2, which satisfies the following conditional expression.
(12) 1.10 <Bfw / (fw × tanωw) <3.50
However,
Bfw: Air equivalent length from the most image-side surface to the image plane at the wide-angle end of the zoom lens ωw: Half angle of view of the most off-axis main ray at the wide-angle end of the zoom lens The focus group constitutes one lens group that moves independently of other lens groups at the time of magnification change, and includes a lens group having a positive refractive power on the object side of the focus group via an air gap. The zoom lens according to any one of claims 1 to 16. The zoom lens according to any one of claims 1 or 3 to 15, which satisfies the following conditional expression.
(13) −0.30 <fF / ft <−0.05
However,
fF: Focal length of the focus group When lens N is a lens that has a negative refractive power and satisfies the following conditional expression,
The zoom lens according to any one of claims 1 to 18, wherein at least one lens N is included after the third lens group.
(14) 15.0 <νdN <42.0
(15) 1.85 <NdN <2.15
However,
νdN: Abbe number on the d-line of the lens N NdN: Refractive index of the lens N on the d-line The zoom lens according to claim 19, wherein the lens N is included in the third lens group. The zoom lens according to any one of claims 1 to 20, and an image pickup element that converts an optical image formed by the zoom lens into an electrical signal are provided on the image side of the zoom lens. An image pickup device characterized by.

Images